The present invention relates to a method of overcoming a delay of signal in an environment in which the signal delay takes place.
As a representative example of generating a signal delay, there is a coordinated multi-point (hereinafter abbreviated CoMP). Specifically, when a receiving stage receives signals from multiple points located physically existing at different locations, the signals received from the multiple points may not be synchronized with each other. For instance, when a base station existing at one location simultaneously transmits signal into multi-cell identified at the corresponding point, timing ambiguity or delay tends not to occur. On the contrary, in case that signals are transmitted/received to/from physically different locations, different delays are experienced while the signals propagate to the physically different locations. Hence, the signals received by the corresponding receiving stage have delay values differing from each other. Moreover, in a downtown area, it is easy to observe that signals arrive at a receiving stage with different delays despite a physically equal distance due to waveguide effect of signal and the like. Due to this reason, it is difficult to implement CoMP (coordinated multi-point) schemes.
The CoMP scheme is usable between macro cells, between macro cell and femto cell or between macro cell and relay node. And, the CoMP scheme is usable to other structural configurations. In an environment for a user equipment transmit/receive signals to/from a plurality of cells, if the signals transmitted from a plurality of the cells have the same delay, CoMP operations are enabled through simple logical signaling.
Yet, if the signals received from a plurality of the cells differ from each other in delay, it is unable to solve the delay differences of the signals received from a plurality of the cells using inter-symbol interference correction in consideration of a delay spread of a single-cell system.
In OFDM system, timing/frequency error considerably affects system performance. Yet, since the CoMP scheme considerably affects the timing error, when a receiving stage receives a signal, performance can be seriously degraded. In order to improve such performance degradation, the receiving stage should implement complicated algorithm.